Don (FPR type), Do you really think it matters in K3 - with micro fan motors and such a simple cage?
If a K3 is setup to run TX RTTY in a controlled environment, and then repeat the test with the fan direction reversed, how much of a temperature delta would you expect? [Elecraft] K3 Cooling Don Wilhelm w3fpr at embarqmail.com Mon Apr 5 15:20:41 EDT 2010 Previous message: [Elecraft] K3 Cooling Next message: [Elecraft] sound card recommendations Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] -------------------------------------------------------------------------------- Don, In my fluid mechanics labs it became apparent that exhaust cooling is much more effective than forced cooling for situations that are similar to the K3 PA 'cage'. First is that the exhaust fan does not add to the temperature of the air, and second, the flow can be more easily controlled. The exhaust fans remove heated air from the hottest spots - who cares where the cooler makeup air comes from, it can be supplied from any vent holes in the cabinet. As humans, this is counter-intuitive because we feel cooler with air blowing onto us, but that is mainly because of evaporation cooling, not air flow. We do not usually feel cooler standing on the other side of a fan. Electronics do not have that evaporative cooling effect (unless you have poured a liquid on the electronics!), so in most cases, exhaust cooling near the heated areas does a better job. If you question the fact that a fan adds heat to the air-stream, measure the temperature on the upstream side of a fan and the downstream side. I can assure you that the downstream air is warmer - the fan provides work to move the air, so it must heat the air because of that work-force (it is not the heat of the fan motor that I am referring to, but the motor heat may be present too. One can design to contain the flow on the downstream side of the fan, but I see no air channel (pipe) in the K3 to accomplish that. With old vacuum tube designs, we often used fans to pressurize the area below the chassis and direct the flow up around the tubes with chimneys around the tubes. 73, Don W3FPR Don Rasmussen wrote: > I've seen this thread on every ham list I've read - goes on forever. > > I always wonder - how does the K3 know which are the intake holes in the > cabinet and which are exhaust? The cool air comes in replacing the hot air, > right? ;-) > > On tube transceivers, the finals may be oriented at the rear of the chassis > near the fan, so a pulling fan will bring the cool air to the finals first, > then that warmed air goes to the rest of the smaller tubes on the chassis. > Reverse the air flow, the finals dont get the room temp air first, the > smaller tubes on the chassis do. This -may- be important on some rigs, guess > it depends. I have the Drakes setup for exhaust. > > K3 has these fins. I am going to take a poll with my fins and find out which > ones care about the direction of the air travelling across them. ;-) > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
